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Studies

Malmö Study

One of the earliest lifestyle intervention studies for the prevention of type 2 diabetes was conducted in men aged 47-49 in Malmö, Sweden. Some IGT and all normal glucose tolerant (NGT) men received usual care, while all type 2 diabetes men and the other glucose intolerant (IGT) men underwent a lifestyle intervention. Of these, approximately 40% of individuals participating in the lifestyle intervention underwent 6-months of supervised physical training and 6-months of dietary treatment in a randomized crossover design. Men who participated in the lifestyle intervention had a lower incidence of type 2 diabetes, and had a greater reversal of glucose intolerance compared to men who received usual care. At the 12 year follow-up, the IGT men who underwent the lifestyle intervention showed no difference in mortality rates when compared to NGT men, and had less than half the mortality rate when compared to IGT men who received usual care.

The Da Qing Study examined the effect of a 6-year diet and exercise intervention in Chinese subjects with IGT and a mean age of 45. The diet intervention alone was associated with a 31% reduction, while the exercise intervention alone showed a 46% reduction in the risk of developing type 2 diabetes. However, the combined diet and exercise group had a similar 42% reduction in the risk of developing type 2 diabetes during a 6-year follow-up period.

Incidence of type 2 diabetes at or before the six year follow-up in the Da Qing study

The Finnish Diabetes Prevention Study (DPS) was the first randomized controlled trial to specifically examine the effect of a lifestyle intervention in preventing type 2 diabetes.17,25 This study randomized 522 overweight/obese subjects with IGT to either a lifestyle intervention or a control group and followed them for approximately 3.2 years. The lifestyle intervention provided individualized counseling focused on achieving and maintaining healthy body weight, reducing fat intake, increasing fibre intake and increasing physical activity. At 2 year follow-up, the incidence of type 2 diabetes in the intervention group was less than half that observed within the control group. Further, the reduction in diabetes was related to the number and magnitude of the lifestyle changes made. Each component of the intervention: weight loss, increase in physical activity, reduction of total and saturated fat intake, and increase in dietary fibre contributed to the risk reduction. More recently, the DPS group have reported that the impact of lifestyle changes in reducing incidence of diabetes was maintained for at least 4 years after the intensive intervention finished.

One of the largest randomized controlled clinical trials to date is the Diabetes Prevention Program (DPP), which was conducted in 3234 US adults with glucose intolerance. Unlike most previous studies, the cohort was diverse and included a large proportion of women (68%) and ethnic minorities (45%), and compared lifestyle intervention versus drug intervention (metformin) and a placebo control group over 2.8 years. The DPP reported that both lifestyle intervention and metformin had positive effects on the prevention of type 2 diabetes and restoring normal glucose tolerance. However, the lifestyle intervention was more effective in preventing type 2 diabetes, particularly in older adults. The lifestyle intervention group also tended to have a lower mortality rate than the metfomin intervention group. The cost-effectiveness of metformin versus lifestyle is highly dependent on the costs of metformin. For example, considering the current generic metformin pricing in the USA, the price of both interventions is comparable.

A recent paper relating to the DPP concluded that an increase in physical activity helps sustain weight loss and independently reduces diabetes risk among those who do not lose weight. Although DPP was not originally intended to examine the metabolic syndrome per se, the DPP report that lifestyle intervention also improves lipid parameters of the metabolic syndrome (fasting triglycerides and high-density lipoprotein cholesterol), and reduced the incidence of hypertension in addition to its positive effect on fasting glucose and glucose tolerance.

The IDPP was a prospective community-based study, that examined whether the progression to diabetes could be influenced by interventions in native Asian Indians with IGT who were younger, leaner and more insulin resistant than populations studied (multiethnic American, Finnish and Chinese populations).28 Results showed that progression of IGT to diabetes is high in native Asian Indians. Both lifestyle modification and metformin significantly reduced the incidence of diabetes in Asian Indians with IGT, there was no added benefit from combining them. The relative risk reduction was 28.5% with lifestyle modification, 26.4% with metformin and 28.2% with lifestyle modification combined with metformin.